If you live in England and are part of the "track and trace" C-19 program, you had to quarantine for 2 weeks if you got a notification, regardless of your vaccination status.

As of today, this is no longer the case for those who are fully vaccinated for at least 2 weeks.

Here's the strange bit;

If you are not part of the program, then you never had to quarantine under the law.

Scotland's program is garbage and barely works. Like with the England program, there is no legal requirement to be a part of the system, thus negating the program's legal requirements.

I have no idea about Wales or Northern Ireland.